<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            background: aqua;
        }
        .m{
            width: 15%;
            margin: 20px auto;

        }
        .as{
            height: 250px;
        }
        .common {
            width:230px;
            height: 30px;
        }
    </style>
</head>
<body >
<div class="as">
    <div class="m">
        <form action="servi" method="get">
            <select class="common"name="select">
                <option value="1">第一行</option>
                <option value="2">第二行</option>
                <option value="3">查询所有</option>
                <option selected="selected" value="wu"></option>
            </select>

            <input type="submit"value="查询" class="common">
        </form>
    </div>
</div>
</body>
</html>